#background {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    min-width: 1000px;
    background-repeat: no-repeat;
    background: linear-gradient(to bottom, #009 0%, #1E9FFF 100%);
    background-size: cover;
    -webkit-background-size: cover;
    -o-background-size: cover;
}

.filter {
    background: #009;
    animation: colorChange 30s ease-in-out infinite;
    animation-fill-mode: both;
    mix-blend-mode: overlay;
    z-index: -2;
}

@keyframes colorChange {
    0%, 100% {
        opacity: .2;
    }
    50% {
        opacity: .7;
    }
}

body {
    text-align: center;
}

.chapter-body {
    margin: 0 auto;
    width: 1200px;
    height: auto;
    background: rgba(255, 255, 255, 0.5);
    border-radius: 15px;
}
.chapter-top {
    width: 100%;
    height: 600px;
    margin: 0 auto;
    margin-top: 50px;
    padding: 30px;
    display: flex;
}

.chapter-top-left {
    width: 40%;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
}

.chapter-top-left img {
    max-width: 100%;
    max-height: 100%;
}

.chapter-top-right {
    width: 60%;
    height: 100%;
    padding: 20px;
    text-align: left;
    word-break: break-word;
}

.chapter-top-right-top {
    width: 100%;
    height: 60%;
    padding-top: 30px;
    overflow: hidden;
}

.chapter-top-right-bottom {
    width: 100%;
    height: 40%;
    display: flex;
}

.chapter-top-right-bottom-left {
    width: 40%;
    height: 100%;
    padding-top: 10%;
}

.chapter-top-right-bottom-right {
    width: 60%;
    height: 100%;
    text-align: center;
}


.chapter-section {
    width: 100%;
    height: auto;
    min-height: 200px;
    padding: 30px;
}
.course-comment {
    text-align: left;
    width: 1200px;
    margin: 0 auto;
    margin-top: 80px;
    margin-bottom: 200px;
    background: rgba(255, 255, 255, 0.5);
    padding: 60px;
    border-radius: 15px;
}

.course-star {
    cursor: pointer;
}

.course-like {
    margin-left: 20px;
    width: 30px;
    cursor: pointer;
}

.course-head {
    width: 75px;
    border-radius: 50%;
    margin-top: 20px;
}

.course-username {
    font-size: 25px;
}

.chapter-list {
    width: 800px;
    margin: 0 auto;
    text-align: left;
}

.course-chapter {
    background: rgba(255, 255, 255, 0.3);
    border-radius: 10px;

}

.course-chapter h1 {
    font-size: 30px;
    padding-left: 20px;
    padding-top: 10px;
}

.course-section {
    padding-left: 40px;
    padding-right: 40px;
}

.section {
    height: 30px;
    cursor: pointer;
}

.section:hover {
    background: #cce5ff;
}

